Apparatus for adjusting a camshaft

ABSTRACT

The invention relates to an apparatus for adjusting a camshaft of an internal combustion engine with at least one electromotor which, by way of a gear, produces the adjustment of the camshaft with respect to a pinion, with the gear comprising a planet cage on which at least one planet wheel is provided which is driven by an electromotor. A rapid adjustment with a simple arrangement at the same time can be achieved in such a way that several planet wheels are provided which are in engagement with a ring gear and that each planet wheel is associated with an electromotor which drives the same via a common shaft.

BACKGROUND OF THE INVENTION

[0001] The invention relates to an apparatus for adjusting a camshaft of an internal combustion engine with at least one electromotor which causes the adjustment of a camshaft towards a pinion by way of a gear, with the gear comprising a planet cage on which at least one planet wheel is provided which is driven by an electromotor.

DESCRIPTION OF PRIOR ART

[0002] An apparatus for adjusting a camshaft of an internal combustion engine is known from EP 0 903 471 A. Its object is to provide the apparatus with a smaller and compacter arrangement and to minimize the problem of tooth flank play.

[0003] U.S. Pat. No. 4,517,934 A discloses a device for adjusting a camshaft, in which an electromotor is arranged on a pinion which is in connected with the camshaft via a gear. The electromotor is supplied with power via slip rings. In order to minimize the occurring balance errors, the electromotor and the gear are arranged on different sides of the camshaft on the pinion. Such an apparatus is complex and the occurrence of inertia forces can be avoided only with difficulty, even in the case of careful design.

[0004] Furthermore, DE 40 40 486 discloses a camshaft adjusting device with a gear which causes the adjustment of the camshaft with respect to the pinion. This gear is adjusted in an embodiment by an axially displaceable rod and in another embodiment by a hydraulic machine which is provided in the pinion. The apparatuses described in said publication are highly complex and very susceptible to malfunction.

[0005] Furthermore, U.S. Pat. No. 5,156,119 A shows an apparatus for changing the valve control times, in which friction wheels are arranged in a pinion which are in connection with a gear arrangement which causes an adjusting movement. By pressing a pair of friction disks against the friction wheels, a change of the valve control times can be achieved.

SUMMARY OF THE INVENTION

[0006] It is therefore the object of the present invention to provide the simplest possible and sturdy apparatus with which an adjustment of the camshaft with respect to the pinion is possible. An electric adjustment is to be provided which shows the lowest possible power consumption. The adjusting gear is to be preferably self-locking so as to make do without power consumption in the stationary operation.

[0007] It is provided for in accordance with the invention that several planet wheels are provided which are in engagement with a ring gear and that each planet wheel is associated with an electromotor which drives the same by way of a common shaft.

[0008] Since in the solution in accordance with the invention several electromotors are switched in parallel and there is a relatively large ratio of transmission, the apparatus can be provided with an exceptionally compact design. A particularly large ratio of transmission with a minimal tooth flank play can be obtained when the planet wheels are arranged as worm wheels and when the ring gear is provided with a helical gearing.

[0009] In a particularly preferred embodiment of the invention it is provided that every worm wheel is driven by two electromotors which are disposed mutually oppositely. A particularly compact arrangement can be achieved in this manner.

[0010] A particularly simple arrangement in a cost-effective design can be achieved in such a way that the electromotors are supplied with power through slip rings.

[0011] A particularly advantageous solution in respect to construction is provided in such a way that the pinion is connected directly with the ring gear. The pinion is preferably provided with an integral arrangement with the ring gear. The apparatus can thus be produced with a particularly compact design.

[0012] As an alternative it is also possible that the camshaft is in connection with the ring gear and that the pinion is in connection with the planet cage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention is now explained in closer detail by reference to embodiments shown in the drawings, wherein:

[0014]FIG. 1 shows a partial longitudinal sectional view sectional of the apparatus in accordance with the invention and

[0015]FIG. 2 shows a sectional view along II-II in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The camshaft adjusting apparatus in accordance with the invention is generally composed of a pinion 10 which can be arranged as a toothed pulley or chain wheel and which, through a gear 12, drives a camshaft 11 on which are arranged cams 13 for actuating inlet and outlet valves (not shown) of the internal combustion engine.

[0017] In the illustrated embodiment the pinion 10 is arranged simultaneously as a ring gear 1 which is provided with a helical gearing 5 which is in engagement with three worm wheels 4. A planet cage 2 is fixedly connected with the camshaft 11, which cage carries six electromotors 3 which are each arranged in pairs on a common axle 3 a with a worm wheel 4 and which drive the same via drive shafts 6. The electromotors 3 are supplied with power through schematically shown slip rings 7 in order to cause the adjusting movement. The pinion 10 is held on the camshaft 11 via a bearing 8 and secured by a screw 9. A further screw 14 secures the fixed seat of the planet cage 2 on camshaft 11.

[0018] The particular advantage of the apparatus in accordance with the invention is that by dividing the actuating moment among several electromotors 3 and by the large transmission ratio which can be achieved by using a ring gear 1 with a respectively large diameter, the load on the individual electromotors 3 is very low. In this way it is possible to achieve an adjustment of the camshaft in a simple and cost-effective manner. In addition to a reduction in fuel consumption and a prevention of emissions which is enabled by the optimization of the internal combustion engine per se, a further reduction in fuel consumption is achieved by the low adjusting energy which is enabled by the apparatus in accordance with the invention. 

What is claimed is:
 1. An apparatus for adjusting a camshaft of an internal combustion engine with at least one electromotor which, by way of a gear, produces adjustment of the camshaft with respect to a pinion, said gear comprising a ring gear; at least two planet wheels engaging with said ring gear; a planet cage bearing said planet wheels; wherein at least one electromotor is connected to each planet wheel by a common shaft which electromotor drives the planet wheel.
 2. An apparatus according to claim 1 , wherein the planet wheels are arranged as worm wheels and that the ring gear is provided with a helical gearing.
 3. An apparatus according to claim 2 , wherein each worm wheel is driven by two mutually oppositely disposed electromotors.
 4. An apparatus according to claim 1 , wherein the electromotors are supplied via slip rings with power.
 5. An apparatus according to claim 1 , wherein the pinion is directly connected with the ring gear.
 6. An apparatus according to claim 5 , wherein the pinion is provided with an integral arrangement with the ring gear.
 7. An apparatus according to claim 1 , wherein the camshaft is in connection with the ring gear and the pinion is in connection with the planet cage. 